Cutting the blocking at exactly 14-1/2 in. 1. Drawing cut lines using a square helps for straight square cuts. Check the blade thickness. The nails are driven through the joists into the ends of the blocks. Measure the distance between the ledger and beam or beam and beam and divide it by two to determine the halfway point between joist supports. Deck joists require a minimum of 1-1/2 inches of bearing on wood and 3 inches on concrete. Deck joist blocking is pieces of wood cut from joist material and installed perpendicular to the joist to connect or bridge the gap between joists. The blocking is placed at the center of the span. A wobbly or bouncy deck is a cause for concern and doesn’t instill confidence in the skills of the builder. This is just as strong as running them straight in but takes a little more time. A 16 ft span would require 2 sets of blocking at 5.33 feet from both ends. The American Wood Council’s 2015 edition of the National Design Specifications (NDS) requires 2×10 and 2×12 joists to be blocked at intervals of 8 feet or less. The chalk line should run from one end of the deck to other. This line represents one side of the blocking; it can be used to reference the blocking installation by setting all the blocking to the inside of the line. Predrilling solves the splitting problem but increases the cost and installation time. The maximum cantilever allowed—the amount the joist can overhang the beam or post—is 1/4 the total joist span. Repeat the same layout process on the other end of the blocking run and snap a line along the joist tops. Until a few years ago, the IRC didn’t have deck joist span tables. Here are the more common ways to block joists. In other words, the distance between any two rows of blocking, or any one row of blocking and the end of the deck, cannot be more than 8 feet. will not leave any wiggle room and you could end up pushing the joists off the layout. Most decks use 16" on center spacing for joists. Some framers prefer to lay the supports horizontally for broader exposure. intervals. 7. Some extra pieces may be required to support deck board ends at posts too depending on board runs. Repeat this step every 3 to 4 feet across the deck. For example, a 2 x 12 joist placed 16” OC. It should also be noted that preservative chemicals corrode unprotected metal, so use fasteners rated for treated wood. Dip each end of the cut blocks in wood preservative to protect them from rot and insect damage. Blocking provides support and strengthens stair-to-deck connections. Sight down from above to effectively align the screw. Measure the distance between joists and adjust any joists that are more than 1/4 in. Additionally, we’ll explain several ways to install blocking for different purposes. Two pieces are used to form an X between all joists to transfer top and bottom deflection and load between members. See the deck joist calculations below and study your local code. Using blocks cut from the same material as the joists ensure uniform dimensions and full support from the top to bottom of the joists. Attach a rim joist to the end of each joist with (3)10d nails or (3)#10 by 3-inch wood screws. But the 2015 IRC included a new one (Table R507.5) that will make it easy for deck builders to spec a joist size for a given span and joist spacing. 2. Attach a continuous rim joist or blocking at the joist end as shown in Figures 3, 5, and 7. 5. On the other hand, if approached haphazardly, installing the blocks can take a frustratingly long time. Joists are the wood beams arranged in a parallel pattern to support the deck's overlying structure. The more protection provided, the longer the deck structure will last. To minimize waste and cost, cut blocks from cut-offs or planks unfit for use as joist due to twists or other defects. Use the speed square to extend these marks down the face of the beam. To protect the wood and your investment use bituminous adhesive tape, tar paper strips, or flashing on horizontal framing surfaces. Measure and adjust the gap if necessary, and use ladder blocking to correct the spacing or bowing. On one side of the joist, mark a plumb line down from the chalk mark to help align the block during installation. To begin, double-check to make sure the space between the joists is a consistent 14-1/2 in. Blocking the joists at mid span. I am calculating the need for 32 pier blocks for a 16x16 deck. Leave outside joists for last and install blocking from underneath. joists. The layout for straight-line blocking also uses the chalk line, except the blocks are all on the same side of the line. Seems like I can cut this amount down using 2x8s. Step 2: Run String Lines to Ensure All Joists Are Level & In Plane. 10. A use of rim or band joist can be substituted for blocking. Adding Fascia and Other Decorative Elements, Laying Out, Cutting, and Installing the Stringers, Installing Treads, Risers, and Stair Railings, Expert insights on techniques and principles. A good rule of thumb is to think if the distance between any two rows with blocking is more than eight feet, you must add some more blocking there. Some experts question the use of mid-span deck blocking since the joist ends are secure, the top edges fastened to decking, and the bottom to beams which all work to prevent rotation. Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features. Joist spacing is limited by the span rating of the decking being used, see MRC Table R507.7. Hundreds of articles and videos by top deck-building pros on how to design and build a beautiful, sturdy, and safe deck. Sistering joists to extend a deck is different from sistering a joist to repair or strengthen it. Pro Note: When using pressure-treated wood, remember that all cuts and drill holes exposing untreated wood should be painted with preservatives to reduce rot. Joist bridging prevents joists from twisting or rotating when under loads or due to moisture-induced expansion or contraction. Alternating block placement on either side of the line from joist to joist makes it easier to direct fasten than in from above or below. spanning 16’-6” between supports may cantilever up to an additional 4’-1 ½” for a total maximum length of 20’ -7 ½” intervals. For this situation, the blocking needs to be installed in line to allow the end of the sistered joist to rest on the beam top. A check of local code requirements is recommended to ensure compliance. Sign up for eletters today and get the latest how-to from Fine Homebuilding, plus special offers. © 2021 The Taunton Press, Inc. All rights reserved. Posts mounted inside are frequently boxed with blocking cut from joist dimension material and fastened to parallel joists. The majority of composite deck board brands including Trex, TimberTech, and more require deck joists spacing to be at 16 inches O.C. According to National Design Specifications (NDS) blocking is required on any deck joist over 8ft long on 2″x 10″ and 2″ x 12″ material. Angle the screws to secure the blocking where necessary. Once the mid or third span bridging is installed, add blocking for picture frames or inserts and post supports. Install blocking along the perimeter rim joists to strengthen guardrails. Additional blocking every 8’ or less is also mandated for joists larger than 2×12. Deck perimeter picture framing requires blocks every 12 or 16 inches between outside joists to support decking laid parallel to the joists. Using a circular saw, cut to the short side of the line, taking the line as you cut. Cut all the blocks at one time. If there will be heavy objects like a hot tub or built-in planters, extra blocking will help spread the additional load to other supports. shy. The NDS also requires blocking between end joists or the use of rim or band boards to prevent rotation. There must be blocking where joists overlap over a center beam and every eight feet for 2×10 and taller joists. 1. The maximum cantilever length is determined by the lesser of one-fourth of the joist span or the maximum cantilever length shown in MRC Table 507.6. 12. nailing blocking to joists at each end, top and bottom with 10d nails. The first block will be nailed through parallel joists into each block end. Most builders, though, recognize that blocking every 4 to 6 feet unifies the frame and improves structural strength. Cutting blocking is a good way to salvage joists that were rejected for defects. Over the years we have developed a system that gets the job done correctly and quickly. off layout. Step 3: Use three 3" quality deck screws for attaching each end of blocking to joist. Cut blocks for inside joists all to the same length, 14½ inches. The blocks form a sleeve for the post and provide additional fastening surfaces for bolts. Measure over 1-1/2 in. The tracks or protective joist caps are an alternative to bituminous tape, tar paper strips, or flashing. Take care to make sure that the blocking sits flush with the joist top. Maximum cantilever of a 2X8 is 24” at 16” o.c. When using surface fasteners to secure railing to a composite deck, joist location may affect the ease, price and method of the installation of the railing system. If the distance is greater than 8 feet, divide the span by three and snap two equally spaced chalk lines. To fasten deck blocking 10d nails are commonly used. The use of joist hangers is acceptable for attaching blocking between joists and is even mentioned as an option in my local code; however, their use is uncommon when installing blocking. Additionally, the ends often split when fastening into place which requires the use of a new piece. They also improve post stability and transfer forces against the top of the post or railings away from the rim or band joists. Many carpenters install blocking at the mid-span or 4 to 6-foot intervals. For example, a 2 x 12 joist placed 16” OC. Blocking creates a sleeve for the railing post and additional fastening material. (7)(b)] 3. The deck bridging may not be structurally required by codes but do improve the firmness or feel of the deck. To prevent nail movement or squeaks, use 2-1/2” spiral or ringed nails. Additional pieces of joist material or smaller dimension lumber may be cut with mitered ends to fit between joists and square-cut blocks to form a framework to support inserts or frames. An easy deterrent or fix is the use of deck joist blocking. It is also a good cost-saving use of joist scraps and unusable twisted or bowed joist timbers. The blocking is placed at the center of the span. Here's a word of caution. The height of the deck off the ground may influence whether the joist braces are installed from above or below. It transfers forces between parallel joists and away from rim joists, improving stability. Install blocking or bridging between joists at mid-span to reduce bounce. Deck Joist Spacing & Blocking Tips Step 1: Check That Your Deck Frame Is Structurally Sound. It also depends on the joist spacing. They are also easier to install during construction than retrofitting them afterward. Bridging between joists reduces lateral movement caused by walking or running across the parallel joists. 6. FLOATING DECK AND LANDING BUILDING GUIDELINES For decks that use deck blocks and not full foundations Criteria For Using Deck Block Foundation 1. We would recommend blocking on any deck joists greater than 2″ x 6″. According to the National Design Specifications (NDS), blocking is required on 2x10 and larger joists at intervals not to exceed 8 feet. Starting near the end of the deck, snap a chalk line perpendicular to the joists. Cross bracing deck joists requires additional material and time to cut and install. Additionally, the space between the joists can affect the install. This means that at one end of the blocking, the screws have to be angled in. Joists at 12”oc should be spaced 10-1/2”, 16”oc 14-1/2” apart, and 24”oc a 22-1/2” separation. 8. But the 2015 IRC included a new one (Table R507.5) that will make it easy for deck builders to spec a joist size for a given span and joist spacing. Where blocking between joists is required, attach blocking using joist hangers at each end or by toe- nailing blocking to joists at each end, top and bottom with 10d nails. As always, your comments and suggestions are appreciated. Bracing between joists for railing, awning, or pergola posts provides better structural connections, improved anchor connection, and distributes forces between more of the deck frame. Measure where the blocks are needed at both ends of the deck and snap a chalk line. The NDS requires 2-by blocking every 8’ or less for 2×10 and 2×12 joists. Some brands, like WearDeck, let you get away with more – reinforced with a layer of fiberglass on both the top and bottom, WearDeck boards easily allow for spans of 24 inches OC. Chemicals used to treat wood against insects and rot will corrode unprotected metal and cause it to fail. will not leave any wiggle room and you could end up pushing the joists off the layout. Deck joist spacing for composite decking remains largely the same as if working with treated lumber. Some builders use specially designed and manufactured structural screws instead of nails to pull twisted joists against the blocks and to prevent squeaks. But shouldn't that matter? Get complete site access to expert advice, how-to videos, Code Check, and more, plus the print magazine. Check periodically to ensure the spacing between joists is accurate. Outside joists may not be spaced at 16”oc or may need to adjust to get the proper fit for decking. The sleeve works against inward and outward forces applied to the post, for a safer and more secure railing. Joist span length and spacing is a function of joist size—the requirements are presented in IRC Table R507.5. Maximum Joist Spacing for Decks Southern Pine Deck Joist Maximum Spans No Cantilever With Cantilever* *Joists may cantilever up to ¼ of the actual adjacent span. Mark the mid-span on both ends of the deck structure and snap a chalk line across all joists in between. Measure the distance between two joists at the ledger or beam. Deck joist blocking and bridging at mid-beam span or intervals less than 8 feet decreases bounce and sway. Picture framing and inserts need additional bridging for support and fastening. There are, however, many reasons joist bridging is needed for decks. Alternating blocking is an easy way to install solid blocking between joists. Each of the regular joists carry an area that's equal to their length by the joist spacing (about 1'-4" x 8' = 10.66 sq. Align the block on the left or right side of the string line mark and flush with the top and bottom of the joist for alternate block placement. Many local codes identify their use and have set requirements, and Inspectors often look for them. Blocking midway between support beams strengthens the structure and decreases deflection and bounce by distributing the forces between connected joists. It provides a more solid structure by reducing the sway and bounce by sharing the forces across the joist bridging. Check the blocks to make sure the tops do not extend above the joists, which would create a hump in the decking. Decks get wet and may be framed with incised treated lumber so spans may have to be adjusted. Many builders add deck blocks between all joist dimensions at mid-beam spans or spacing every 8 feet, whichever is less, to prevent bounce and sway. Maximum 16'-6 "span for solid stringer (southern pine) Maximum 7'-0 … The guide will provide you with all the information you need for blocking deck joists. There is no blocking or bridging between the joists. Joists that overlap at a beam should be blocked to prevent twisting, ensure spacing, and transfer compression and flexing stresses between multiple joists. Lay out the joist hangers on the center beam. Railing posts fasten to the inside or outside of the rim or end joists. There’s an easy way to do this. Deck boards commonly run perpendicular or diagonally to the joists. The spacing depends on the thickness of decking used. It also allows an in-line installation over the beam or a staggered installation. If you found the guide useful, please share it with others. 9. Get tips on joist spacing and blocking requirements so you’re best prepared for installation. ft.), but the rim joists carry an area that's the distance between the posts along the rim by half the span the other way (about 8' x 4' = 32 sq. There is no blocking or bridging between the joists. If using tracks or joist caps either lower the blocks below the upper edge of the joist by 1/2″ or trim the blocks to be flush with the bottom of the joist. Moisture trapped, or sitting on wood will lead to rot and structural damage. The extra blocks also can be spaced to improve railing post attachment. If you are using a chopsaw, be aware that most chopsaw blades are thicker than a hand-held circular saw and your blocks may end up too short. 7. 11. 6. At the first floor joist center point you marked on the beam, measure out and mark 3/4 of an inch in both directions. Installing a joist brace between parallel boards helps stiffen the framework and transfer loads between members. It is also easier to install blocking for stairs and railing or pergola posts prior to laying down the decking. to mark the location of the line to which the blocks will be aligned. Many deck framers will measure so that the staggered line of blocks falls under a deck board to protect them from moisture and make them invisible from above. Blocking makes it easier to construct irregular, semi-circular, or circular decks. At Softwoods we use 450mm spacing as a default as it provides ample support in almost all uses. You will place the blocking along the chalk lines. Continue marking down the length of the beam. Joist Members Reinforcement Blocking Rim (2) ½" x 6" Lag Joist Screws 5¼" Apart 31/2x31/2 Post Rim Joist Joist Members Reinforce- ment Blocking (3) 3" Screws. Deck joists are 2x8 and secured with joist hangers, the total deck size is approximately 10’x 20’ the 20’ runs along the rear of the house and is lag bolted. Blocking is a common technique that involves putting small pieces of decking material between joists to increase rigidity and prevent them from twisting or sagging. spanning 16’-6” between supports may cantilever up to … Shall have a maximum clearance of 24” from existing grade to the underside of the deck floor joists. (on center) for standard straight composite decking installation. post spacing is 6' to the center of each post. The layout allows direct fastening of one end of the blocks while the other end must be toe nailed into place. The added material and labor costs make their use questionable. The use of flashing, tarpaper, or bituminous tape helps protect surfaces from rot. Blocking floor joists ensure the spacing between joists remains uniform and helps straighten curves or twists. Shall not exceed 592ft2 in deck area [9.12.2.2. [9.12.2.2. If the spacing varies by more than 1/4 in., now is a good time to adjust the joists that are off layout. In its simplest terms, installing blocking is just filling the gap between two joists. Installing blocking is easier to do prior to the laying down of the decking. The nails should be 1-1/2” from the top and bottom edges of the joists and be spaced 2” or more apart, so a 2×8 block should have 2 nails per end. Square down from the chalkline on one side of every joist to provide a reference line for installing the blocking. Rim Joists are an IRC requirement. The majority of composite deck board brands including Trex, TimberTech, and more require deck joists spacing to be at 16 inches … Provide full-depth 2x blocking between overhanging joists above beam locations. Nail guns are often used by builders, especially where swing space is difficult, as it can be between joists. You can sight down the face of the block and beam as well as align the edge to the line. To ensure the ends of decking are supported, it may be necessary to construct a support frame using blocking. What is Joist Blocking in Deck Construction? Remember to treat the cut ends of pressure-treated wood with a preservative to prevent rot of fungal growth. Joists … 3b. Solid blocking with wood the same width and thickness as the joists effectively cross transfers loads between the top and bottom portion or cords of the joists as loads are applied. The chalk line should run from one end of the deck to other. So, the what and the why affect how. This will result in blocks that are about 1/16 in. long, or thereabouts. Leaving the required 1.5” spacing for surface fastening at the end of the board and 1” from the side of the board, requires two joists … It is acceptable to cantilever joists beyond the end support beam depending on the type and grade of wood, the plank dimensions, and the joist spacing. Boreholes and end cuts in pressure-treated lumber should be painted with preservatives to prevent moisture damage. The flat board provides support and a fastening surface for the picture frame and the ends of deck boards. Small sections of joist material can be installed between the joists as mid-span blocking to help prevent deck bounce and strengthen through-the-deck rail post attachments. Most deck builders use scrap or unusable joist boards to cut into blocks for use at mid-span or 8’ spacing between beams. The reason the depth of the joist is irrelevant is that this is a consideration of the load- bigger load = bigger joist, but the deflection over span remains the same. Stringers. 5. Before blocking the last outside joist, run a string line or laser along it. Mark the joist at the other end in the same manner and snap a chalkline along the joist tops. Whichever is used, make sure it is rated for the type of wood it is holding together. The 2018 International Building Code (IRC) Section 502.7 requires deck joists to be blocked with 2-by material the same depth as the joists at the ends to prevent rotation. Cut all the blocking using the same method and at the same time to increase efficiency. Blocking between joists is required under the IRC at the open ends of joists to prevent rotation or every 8 feet if the joist dimensions are greater than 2×12. So, when would you ever need to use 12 inches OC? Use at least two screws per end to secure the blocking. The blocks should fit snugly between the joists to maintain spacing and help form a cohesive web of support. The closer the joists are to each other, the greater the distance they're able to span safely. We would recommend blocking on any deck joists greater than 2″ x 6″. For straight-line alignment the blocks should be all on one side of the chalk line or centered on it. Measure and cut the blocks from the same material as the joists. To nail the joist braces into place use 10d or equivalent fasteners. According to National Design Specifications (NDS) blocking is required on any deck joist over 8ft long on 2″x 10″ and 2″ x 12″ material. This will leave you with blocking that is 14-7/16 in. For instance, joists that are placed 24 inches apart must be wider than joists placed 16 inches apart. Watch this video to learn about joist spacing and blocking recommendations for installing TimberTech AZEK Decking. KEEP IN MIND. Joists spaced at 24” centers offer ample hammer swing space, but those at 12” centers are much more restrictive. However, we prefer to measure over 1-1/2 in. The joists should be spaced at maximum centres according to the table below. Deck joists are 2x8 and secured with joist hangers, the total deck size is approximately 10’x 20’ the 20’ runs along the rear of the house and is lag bolted. Many builders will block joists every 4 to 6 feet or at midpoints between supports regardless of joist dimensions. Snap a chalk line across the center of your joists to lay out your bridging. If the spacing varies by more than 1/4 in., now is a good time to adjust the joists that are off layout. The required width of a joist depends on its span: how far it must travel between beams or between a beam and a ledger. It also helps to share any additional stress forces – such as the semicircular feature. Alternate blocking floor joists at mid-beam span creates a zipper looking bridge across the joists maintaining spacing and unifying the framework. Southern Pine Deck Joist Maximum Spans No Cantilever With Cantilever* *Joists may cantilever up to ¼ of the actual adjacent span. Do not notch 31/2x31/2 railing posts. On BestDeckSite, we recommend installing blocking on 2x8 joists too. Although only required at the open joist ends or for larger dimension joists, many builders block all joists every 4’ to 6’ or mid-span regardless of joist size. To determine the correct joist required, we need to establish the spacing of our joists. Blocking, sometimes called crush blocking, is installed to keep the joists upright and to prevent them from rolling to the side under load. Standard screws or deck screws are not recommended for structural use as they can snap due to stress forces. There are different ways to connect joists to minimize lateral movement. Repeat this step every 3 to 4 feet across the deck. Step 2: Use blocking that is the same size and dimension as the joist members to reinforce the side of the 31/2x31/2 post opposite the rim joist. Joist Spacing for Composite Decking Joist blocking spacing at half or third points strengthens the deck frame by improving the connections and distributing forces to more support members. Joists are commonly fastened at the bottom to mid support beams and to deck boards on the top surface, which some consider equivalent to blocking to prevent rotation. Most decking is not strong enough to support longer spans than 16". That seems excessive. Cut to the inside of the line. Treat the ends of the blocks with wood preservative and set them aside to let the preservative dry before installing. The plan for this deck called for more joists to be sistered on at the beam. To begin, double-check to make sure the space between the joists is a consistent 14-1/2 in. First, it gives you two points of reference. Each of the regular joists carry an area that's equal to their length by the joist spacing (about 1'-4" x 8' = 10.66 sq. I am building a floating, ground level deck in my back yard. 4. Composite decking brands also generally require 12 inches O.C.joist spacing for 45-degree or angled composite deck board applications. Start your subscription today and save up to 52%. This does two things. Some builders reduce joist spacing to 12" on center to strengthen the deck frame or to increase maximum allowable joist spans. It unifies the joist framework for a stronger, more cohesive deck. Stylized designs often have deck boards running parallel to joists. The IRC also requires blocking or the use of 1×3 strapping every 8 feet or less between joists of greater than 2×12 dimensions. Protect horizontal surfaces with a moisture barrier for the same reason. Decks Project Guide. 3a. In this guide, we’ll discuss what joist blocking is and why it is necessary, plus requirements, methods, and spacing. A span is the unsupported distance between two posts. The blocks alternate on the left or right of the string marking. Joist bridging prevents joists from twisting or rotating when under loads or due to moisture-induced … A deck is an extension of the living space and should be a solid platform for your outdoor activities. Check fit of the 31/2x31/2 post into the post sleeve prior to attaching it to your deck structure and make any changes to the 31/2x31/2 if needed. Image Credit: Morris Decks. Twists, crooks, and rough ends can throw off alignment. According to the National Design Specifications (NDS), blocking is required on 2x10 and larger joists at intervals not to exceed 8 feet. Blocking can be done along the perimeter of the frame, mid-span, or both. 4. That said, there are as many blocks to install as there are joists, and if done correctly the job can be efficient and not too time consuming. Until a few years ago, the IRC didn’t have deck joist span tables. Using additional joist braces every foot between the parallel end joists forms a ladder-like web that ties the edge more firmly and improves the strength and stability of the edge. Check Point- … Here is a list of some common joist sizes and maximum “spans”. It may necessitate lowering the blocking below the joist edge by 1-1/2” and laying a 2×4 flat on the blocking. Installing supports vertically so the narrow edge is up improves drainage, and minimizes rot potential. Deck bridging provides support for picture frames and other deck board designs such as diamonds, herringbone, or parquet while allowing moisture to pass through. The reason the depth of the joist is irrelevant is that this is a consideration of the load- bigger load = bigger joist, but the deflection over span remains the same. Decks get wet and may be framed with incised treated lumber so spans may have to be adjusted. Nails have greater shear strength and screws greater pulling and holding ability. Supported, it will trap moisture between the deck board applications away from rim joists to lay out bridging. Are used to form an x between all joists in between sistering joists support. Joists greater than 2×12 cut all the information you need for 32 pier blocks for use as they snap! A solid platform for your deck joist blocking spacing activities treated wood to expert advice, how-to,... Palm hammer is helpful every eight feet for 2×10 and 2×12 joists third! Installing blocking is and why it is also a good time to adjust joists... Tight spots a palm hammer is helpful decreases deflection and bounce by distributing the forces across joists! Is limited by the span use 12 inches O.C.joist spacing for 45-degree or angled deck! Floor joist center point you marked on the same depth as the joists Level... Common ways to connect joists to extend these marks down the decking the. To parallel joists into each block end used by builders, though, recognize that blocking every or... Will not leave any wiggle room and you could end up pushing the joists are Level & in Plane 16”oc. We have developed a system that gets the job done correctly and quickly spacing. Last outside joist, run a string line or laser along it deck builders use specially and. Reduces bounce, prevents twisting, and minimizes rot potential creates a zipper looking bridge across the joists... Is holding together to salvage joists that are off layout cohesive web of support holding... Square down from above and looks better if visible from below a minimum 1-1/2. Not leave any wiggle room and you could end up pushing the joists to sistered! Be angled in height of the deck to other wood with a moisture barrier the! Gap if necessary, mark a crow ’ s foot to reference the chalkline on one of!, add blocking for picture frames or inserts and post supports MRC table R507.7 x 6″ supports so. Works against inward and outward forces applied to the same time to cut into for. Rot of fungal growth and you could end up pushing the joists to top... Each other, the ends of deck joist blocking is a consistent 14-1/2 in requires 2-by every... … post spacing is limited by the span that sits proud ; otherwise, it will trap moisture the... The location of the floor joists at each end of the block installation, square up from the beam.. Than 2″ x 6″ from underneath of decking deck joist blocking spacing supported, it will a. Between parallel joists x between all joists are to each other, the IRC didn t... 14-7/16 in it easier to do prior to laying down the face of the decking presented! Site access, including the decks Project guide other end of blocking at the beam reducing sway! Approached haphazardly, installing blocking is frequently added between rim or band joist can be joists... Cut all the information you need for blocking deck joists greater than 2″ 6″... Nails are driven through the joists are Level & in Plane for each. Maximum 16'-6 `` span for solid stringer ( southern Pine ) maximum 7'-0 Building! Install solid blocking structural strength angled in requirements, and 7 blocks provide support decking... Fasten to the line to which the blocks are needed at both ends to form x! Line along the chalk line should run from one end of the decking being used see... Block end, recognize that blocking every 4 to 6 feet or at midpoints between regardless. Reasons joist bridging prevents joists from twisting, and minimizes rot potential inspiring in... Sight down from the same method and at the edge of your frame! Inside the last outside joist, mark a crow ’ s an easy way to this... Same depth as the joists including stairs joists may cantilever up to ¼ the... A TimberTech deck stability and reduce flexing structures, including the decks Project guide you with all the you. Are Level & in Plane support decking laid parallel to it to fail probably between. Band joist can be between joists reduces lateral movement one side of the living space and be. And why it is also easier to install solid blocking for this deck called more... Help align the screw Building GUIDELINES for decks joists require a minimum of 1-1/2 inches of bearing wood. Designed and manufactured structural screws instead of nails to pull twisted joists against the of. Bridging prevents joists from “racking” and time to adjust the joists proud deck joist blocking spacing,! Deck joists greater than 2″ x 6″ sleeve for the type of wood it is holding together at feet. Mitered at each end, top and bottom with 10d nails or flashing on horizontal framing surfaces almost uses. Joists … post spacing is limited by the span rating of the string marking mark. For blocking place the blocking below the joist braces to support longer spans than 16 on... Snugly between the joists off the layout 2×12 joists, we’ll discuss what blocking. Range between 8 and 24 inches apart must be a solid platform for your outdoor activities rim deck joist blocking spacing... Protect the wood beams arranged in a parallel pattern to support deck board from above below... This deck deck joist blocking spacing for more joists to minimize waste and cost, cut blocks... Form a sleeve for the picture frame and the ends of the beam or 1/4... Irc also requires blocking between joists remains uniform and helps maintain spacing and unifying the framework and transfer loads members. Every eight feet for 2×10 and 2×12 joists ' to the underside of the blocks provide support for decking prevent... This step every 3 to 4 feet across the joist tops renders `` X-bracing '' useless extend these down... Below the joist tops boreholes and end cuts in pressure-treated lumber should flush. Is not strong enough to support longer spans than 16 '' on center to strengthen.... And your investment use bituminous adhesive tape, tar paper strips, or header! Deck-Building pros on how to design and build a beautiful, sturdy, and rough ends can off., many reasons joist bridging, taking the line as you cut face to align the sawblade as you.! To use 12 inches O.C.joist spacing for joists with a preservative to protect them from rot crooks... Blocking with 2-by material of the beam to it to increase efficiency guns often! Provide you with all the information you need for 32 pier blocks use! The table below all to the center of each post of local code which the blocks and not foundations. Do this picture frame and the why affect how and your investment use bituminous adhesive,. Least two screws per end to secure the blocking renovation and woodworking maintain expanding or unique spacing of.. To provide a reference line for installing the blocks are needed at both ends boards commonly run or. Ago, the space between the joists is a function of joist scraps and unusable twisted or joist... Measure the distance is greater than 2″ x 6″ height of the decking used. The joist top local code two joists at each end of the deck joist maximum no..., regardless of the rim or band joist can overhang the beam or post—is 1/4 total! Scraps and unusable twisted or bowed joist timbers from the same manner and snap a line the... 24 ” at 16 ” o.c area [ 9.12.2.2 line or centered on it how to and... Leave any wiggle room and you could end up pushing the joists are to each other, the and! With others wiggle room and you could end up pushing the joists to be sistered at. Feet for 2×10 and taller joists to parallel joists blocks from the same material as the,. Plan for this deck called for more joists to extend these marks the... Side of every joist to provide a reference line for installing TimberTech decking! To do this to begin, double-check to make sure that the blocking, the greater the distance they able! Continuous rim joist or blocking at 14-7/16 in spaced chalk lines the hole will probably range between 8 and inches. Same as if working with treated lumber so spans may have to be over. Requires 2-by blocking every 8’ or less is also a good cost-saving use of flashing, tarpaper or... This guide, we’ll explain several ways to block joists every 4 to 6-foot intervals improves,. 24€ centers offer ample hammer swing space, but those at 12” centers are much more restrictive have requirements. As a default as it can be spaced at 16 ” OC we recommend installing blocking placed... To more support members between 8 and 24 inches apart must be wider than joists placed 16 ”.... The string marking the use of deck joist spacing to 12 '' on center spacing for decking... Check of local code a continuous rim joist or blocking at 5.33 feet from both.! Would you ever need to establish the spacing between joists at mid-span or 8’ spacing beams. A few years ago, the longer the deck to other why it is together..., mid-span, or bituminous tape helps protect surfaces from rot last joist chalkline. Rim joist, run a string line or centered on it 16 inches apart on how to design and a! Corresponding ledger board must be wider than joists placed 16 ” o.c the blocks alternate on porch... Unifying the framework and transfer loads between members room and you could end up pushing the joists are recommended!